docs: def format_symbol(symbol):
      """Returns well formatted Hermann-Mauguin symbol as extected by
      the database, by correcting the case and adding missing or
      removing dublicated spaces."""
      fixed = []
      s = symbol.strip()
      s = s[0].upper() + s[1:].lower()
      for c in s:
          if c.isalpha():
              fixed.append(' ' + c + ' ')
          elif c.isspace():
              fixed.append(' ')
          elif c.isdigit():
              fixed.append(c)
          elif c == '-':
              fixed.append(' ' + c)
          elif c == '/':
              fixed.append(' ' + c)
      s = ''.join(fixed).strip()
      return ' '.join(s.split())